The present invention pertains to a vertical hydraulic press apparatus adapted to most efficiently and effectively cause complementary half-molds to clamp together in both, processes used to form metal materials and processes aimed at injection-molding and forming thermoplastic materials.
A very wide variety and types of hydraulic press apparatuses are largely known to be currently available and in practical use. It can be easily noticed that simplicity in overall construction of such machines, and an easy and effective as possible control of operations thereof are among the most common requirements that engineers tend to comply with when designing these presses.
A basic schematic layout of a hydraulic press apparatus used for clamping half-molds during injection-molding processes for forming thermoplastic materials generally includes a guide column associated with a piston adapted to slide within a hydraulic cylinder. When an upper half-mold is moved vertically with respect to a stationary lower half-mold, hydraulic fluid that finds itself on a side of the piston is partially transferred, owing to displacement of the piston itself, to another side of the piston through an external circuit and at least a controlled valve.
Presence of such an external circuit, however, implies installation of a number of mechanical component parts, and further requires many precision machining operations to be performed. Such a need, along with requirements for the valve and related control circuits, make construction of such a press apparatus particularly complicated, expensive and demanding, and also quite delicate in its operation.
U.S. Pat. No. 5,204,047 and U.S. Pat. No. 5,302,108 are known to teach a method for making a particular type of hydraulic press apparatus using a support column for pistons so as to minimize overall space requirements of the press apparatus, wherein peculiarity of this press apparatus lies in its being provided with a plurality of pistons associated with a stationary differential piston.
Although a main purpose of the above two patents is actually reached with such a solution, the press apparatus of these patents is too complicated and expensive in its construction and delicate in its operation because of, particularly, a large number of hydraulic conduits that need to be closed and opened in a synchronized pattern.
It is therefore a main purpose of the present invention to provide a vertical hydraulic press apparatus, particularly adapted for use in connection with plastic molding processes, which apparatus is compact, reliable in its operation, uses low-cost materials, construction requirements and component parts, and has a simple and reliable construction based on use of readily available techniques.
Such a type of press apparatus is obtained and implemented with features that are substantially described with particular reference to the appended claims.